The Commonwealth of Australia Constitution Act 1900 (Imp) became law on 9 July 1900, and entered into force on 1 January 1901. Even though the Constitution was originally given legal force by an Act of the United Kingdom parliament, the Australia Act 1986 removed the power of the United Kingdom parliament to change the Constitution as in force in Australia, and the Constitution can now only be changed in accordance with the prescribed referendum procedures in Section 128.

Other pieces of legislation have constitutional significance for Australia. These are the Statute of Westminster, as adopted by the Commonwealth in the Statute of Westminster Adoption Act 1942, and the Australia Act 1986, which was passed in equivalent forms by the United Kingdom Parliament and the Australian Federal Parliament (using legislative powers conferred by enabling acts passed by the Parliaments of every Australian state). The Statute of Westminster Adoption Act is often regarded as the point at which Australia became, de jure, an independent nation, while the Australia Act severed the last remaining constitutional links between Australia and the United Kingdom. Even though the same person, Queen Elizabeth II, is the monarch of both countries, she acts in a distinct capacity as monarch of each.[2]

The history of the Constitution of Australia began with moves towards federation in the 19th century, which culminated in the federation of the Australian colonies to form the Commonwealth of Australia in 1901. However, the Constitution has continued to develop since then, with two laws having particularly significant impact on the constitutional status of the nation.

In the mid-19th century, a desire to facilitate co-operation on matters of mutual interest, especially intercolonial tariffs, led to proposals to unite the separate British colonies in Australia under a single federation. However, impetus mostly came from Britain and there was only lacklustre local support. The smaller colonies feared domination by the larger ones; Victoria and New South Wales disagreed over the ideology of protectionism; the then-recent American Civil War also hampered the case for federalism. These difficulties led to the failure of several attempts to bring about federation in the 1850s and 1860s.

By the 1880s, fear of the growing presence of the Germans and the French in the Pacific, coupled with a growing Australian identity, created the opportunity for establishing the first inter-colonial body, the Federal Council of Australasia, established in 1889. The Federal Council could legislate on certain subjects, but did not have a permanent secretariat, an executive, or independent source of revenue. The absence of New South Wales, the largest colony, also diminished its representative value.

Henry Parkes, the Premier of New South Wales, was instrumental in pushing for a series of conferences in the 1890s to discuss federalism – one in Melbourne in 1890, and another (the National Australasian Convention) in Sydney in 1891, attended by colonial leaders. By the 1891 conference, significant momentum had been built for the federalist cause, and discussion turned to the proper system of government for a federal state. Under the guidance of Sir Samuel Griffith, a draft constitution was drawn up. However, these meetings lacked popular support. Furthermore, the draft constitution sidestepped certain important issues, such as tariff policy. The draft of 1891 was submitted to colonial parliaments but lapsed in New South Wales, after which the other colonies were unwilling to proceed.

In 1895, the six premiers of the Australian colonies agreed to establish a new Convention by popular vote. The Convention met over the course of a year from 1897 to 1898. The meetings produced a new draft which contained substantially the same principles of government as the 1891 draft, but with added provisions for responsible government. To ensure popular support, the draft was presented to the electors of each colony. After one failed attempt, an amended draft was submitted to the electors of each colony except Western Australia. After ratification by the five colonies, the Bill was presented to the British Imperial Parliament with an Address requesting Queen Victoria to enact the Bill.

Before the Bill was passed, however, one final change was made by the imperial government, upon lobbying by the Chief Justices of the colonies, so that the right to appeal from the High Court to the Privy Council on constitutional matters concerning the limits of the powers of the Commonwealth or States could not be curtailed by parliament. Finally, the Commonwealth of Australia Constitution Act was passed by the British Parliament in 1900. Western Australia finally agreed to join the Commonwealth in time for it to be an original member of the Commonwealth of Australia, which was officially established on 1 January 1901.

Although Federation is often regarded as the moment of "independence" of Australia from Britain, legally the Commonwealth was a creation of the British Parliament, through the Commonwealth of Australia Constitution Act 1900 (Imp), which applied to Australia by paramount force. As a result, since Australia was still legally a colony, there was continued uncertainty as to the applicability of British Imperial laws to the Commonwealth. This was resolved by the Statute of Westminster 1931, adopted by the Commonwealth via the Statute of Westminster Adoption Act 1942. The Statute of Westminster freed the Dominions, including the Commonwealth, from Imperial restrictions. Legally, this is often regarded as the moment of Australia's national independence.

However, due to specific exemptions in the Statute of Westminster, Imperial law continued to be paramount in Australian states. This was altered by the Australia Act 1986, which was passed in substantially the same form by the Commonwealth parliament and the British parliament, at the request of each state. In addition to ending the British Parliament's power to legislate over Australian states, the Australia Act also cut the last avenues of appeal from the Australian courts to the Judicial Committee of the Privy Council. As a symbol of the significance of this legislation, Queen Elizabeth II travelled to Australia to personally sign the proclamation of the law.

For the Constitution, the impact of these two laws is that the Constitution as in force in Australia is now separate from the text in the original Act. While the British Parliament can amend or repeal the Imperial Act, that would not affect Australia. Instead, the Constitution as in force in Australia can only be amended following the referendum mechanisms set out in the Constitution. Conversely, any amendment to the Constitution in Australia following the referendum mechanisms would not affect the text of the Imperial Act as in force in the United Kingdom.

The Commonwealth of Australia Constitution Act 1900 (Imp) contains a Preamble, and nine sections. The legislative, executive, and judicial powers are separately stated in the Constitution, in Chapters I, II and III respectively.[5] Sections 1 – 8 are covering clauses outlining the legal procedures for the establishment of the Commonwealth. Section 9, beginning with the words "The Constitution of the Commonwealth shall be as follows ...", contains the Constitution of the Commonwealth of Australia. The Constitution itself is divided into eight chapters, containing 128 sections.

Part II of this chapter deals with the Senate. Senators are to be "directly chosen by the people of the State", voting as a single electorate. Each Original State is to have the same number of senators. Currently, there are 12 senators for each State, and 2 each for the mainland territories, the Northern Territory and the Australian Capital Territory.

Part III deals with the House of Representatives. As nearly as practicable, Section 24 requires the House to be composed of twice as many members as the Senate, each elected by a single electorate. This is the so-called 'Nexus', which is designed to prevent swamping of the senate's power in the case of a joint sitting (see Section 57 below). The number of electorates in a State is to be (roughly) proportional to its share of the national population.

Part IV ("Both Houses of the Parliament") deals with eligibility for voting and election to the parliament, parliamentary allowances, parliamentary rules and related matters.

Part V deals with the powers of the parliament. Section 51 deals with powers of the Commonwealth parliament and are called "specific powers". These contain "concurrent powers", in the sense that both the Commonwealth and States can legislate on these subjects, although federal law prevails in the case of inconsistency (Section 109). Of the thirty-nine elements of section 51, a few have become critical in determining the scope of Commonwealth government action, including the Trade and Commerce Power, the Corporations Power and the External Affairs Power. Section 52 deals with powers exclusively vested in the Commonwealth parliament. States cannot legislate on these subjects.

Chapter II sets up the executive branch of government. Executive powers are exercised by the Governor-General, advised by the Federal Executive Council. Under this Chapter, the Governor-General is the commander in chief, and may appoint and dismiss the members of the Executive Council, ministers of state, and all officers of the executive government. These powers, along with the powers to dissolve (or refuse to dissolve) parliament (Section 5, Section 57), are termed "reserve powers", and their use is dictated by convention. Generally, the Governor-General acts only on the advice of the Prime Minister. One notable instance of the Governor-General acting outside the advice of the Prime Minister of the day, when Governor-General Sir John Kerr, acting on his own authority, dismissed Prime Minister Gough Whitlam in the 1975 Australian constitutional crisis.

Reserve powers in all Westminster nations are only extremely rarely exercised outside of the understood conventions. However, in contrast with the constitutions of other Commonwealth realms such as Canada which formally grant extensive reserve powers to the Monarch, even the formal powers of the Queen of Australia are extremely limited, and most powers are only exercisable by the Governor-General.

Section 68 states that the command of Australia's naval and military forces is vested in the Governor-General as the Queen's representative. This role, however, is only formal (such as the commissioning of officers) and ceremonial; actual control of the armed forces rests with the government.

Chapter III sets up the judicial branch of government; its provisions create the federal judicature and define the way it operates. Section 71 vests judicial power in a "Federal Supreme Court" to be called the High Court of Australia, and such other federal courts as Parliament creates, and in such other courts as Parliament invests with federal jurisdiction. Such courts are called "Chapter III Courts" and are the only courts that can exercise federal judicial power. Sections 73 and 75–78 outline the original and appellate jurisdiction of the High Court. Section 74 provides for the circumstances in which an appeal can be made to the Queen in Council. Section 79 allows Parliament to prescribe the number of judges able to exercise federal jurisdiction and section 80 guarantees trial by jury for indictable offences against the Commonwealth.

Chapter IV deals with finance and trade in the federal system. Section 81 prescribes that all Commonwealth revenue shall form the Consolidated Revenue Fund. Parliament can make laws as to the appropriations of money (Section 53). Unlike most other powers of the parliament, laws made under the appropriations power are not ordinarily susceptible to effective legal challenge. Section 90 gives the Commonwealth exclusive power over duties of custom and excise.

Section 92 provides that "trade, commerce, and intercourse among the States shall be absolutely free". The precise meaning of this phrase is the subject of a considerable body of law. Some of the most recent case law has emphasised that Section 92 is preoccupied with the effect of law on interstate trade, not on the effect law has on individual traders.[6]

Section 96 gives the Commonwealth power to make grants to States "on such terms and conditions as the Parliament thinks fit". This power has been held to be unconstrained by any other provision, such as Section 99 which forbids giving preference to one State or part thereof over another State or part thereof. It is subject only to Section 116, freedom of religion, and possibly other such freedoms. This power, although evidently envisaged as a temporary measure ("during a period of ten years ... and thereafter until the Parliament otherwise provides"), has been used by the Commonwealth to encourage co-operation by the States to various extents over the years.

Section 101 sets up an Inter-State Commission, a body which is now defunct, but which was originally envisaged to have a significant role in the federal structure.

Chapter V contains provisions dealing with the States and their role under the federal system. Sections 106–108 preserves the Constitution, powers of the Parliament, and the laws in force of each of the States.

Section 109 provides that, where a State law is inconsistent with a federal law, the federal law prevails (to the extent of the inconsistency).

Section 111 provides that a State can surrender any part of the State to the Commonwealth. This has occurred on several occasions, most notably the surrender by South Australia to the Commonwealth of the Northern Territory.

Section 114 forbids any State from raising a military force, and also forbids the State or the Commonwealth from taxing each other's property.

Section 116 establishes what is often called "freedom of religion", by forbidding the Commonwealth from making any law for the establishment of a religion, imposing any religious observance, or prohibiting the exercise of a religion, or religious discrimination for public office.

Chapter VI allows for the establishment or admission of new states. Section 122 allows the Parliament to provide for the representation in Parliament of any territory surrendered by the States, or placed by the Queen in the authority of the Commonwealth. Section 123 requires that changing the boundaries of a State requires the consent of the Parliament of that State and approval by referendum in that State.

No new states have been admitted to the Commonwealth since federation.

Chapter VII contains three quite different provisions. Section 125 provides that the seat of government of the Commonwealth would be in Melbourne for the time being, but eventually in Commonwealth territory, to be created within New South Wales but no less than one hundred miles from Sydney. The national capital would thus be neither of the rival State capitals Sydney and Melbourne, but within a federal territory. In 1911 New South Wales ceded to the Commonwealth what is now the Australian Capital Territory and Canberra, built within it, was declared the national capital in 1913. Section 126 permits the Governor-General to appoint deputies. Section 127 provided that "aboriginal natives" were not to be included in any Commonwealth, State or other count of population. This excluded the Indigenous population from affecting the distribution between the States of seats in the House of Representatives (section 24). Section 127 was removed by referendum in 1967.[7]

Chapter VIII specifies the procedures for amending the Constitution. Section 128 provides that constitutional amendments must be approved by a referendum. Amendment requires:

approval of a referendum bill, containing the proposed amendment, by an absolute majority in each house of the federal parliament; and then

approval of the bill in a referendum, by a majority of electors in each of a majority of the States (that is, in at least four of the six States), as well as a majority nationwide (that is, comprising voters in both States and Territories); the franchise in a referendum is to be the same as that in an election to the House of Representatives.

The Governor-General must put the bill to a referendum between two and six months after it has been passed by the parliament. If the bill is approved in the referendum, it receives the Royal Assent and becomes law, so that the wording of the Constitution is changed.

An exception to this process is if the bill is approved by only one house of the parliament—the other house rejecting it, failing to pass it or passing it with amendments to which the first house does not agree. (Ordinarily, the bill would have been introduced in the House of Representatives; the problem would be disagreement by the Senate.) Then, after three months, the first house may pass the bill again. If the other house still does not agree with the bill, then the Governor-General may put the bill to a referendum in the form in which it was passed by the first house, with any amendments to which the two houses may nevertheless have agreed.

Section 128 also provides that an amendment that would reduce the representation of a State in either house, or its minimum representation in the House of Representatives, or that would alter the boundaries of a State or make any similar change to the State, can be presented for Royal Assent only if it has been approved in that State.

A mechanism for the conduct of a referendum is provided by federal statute: Referendum (Machinery Provisions) Act 1984 (Cth).[8] As with elections, voting is compulsory.

The Schedule sets out the wording of the oath and the affirmation of allegiance. The Governor-General and members of parliament are required to make a solemn undertaking of allegiance, by oath or affirmation as prescribed by the Constitution. In addition, when taking office, the Governor-General is required to take an oath of office, currently:

I, (name), do swear that I will well and truly serve Her Majesty Queen Elizabeth the Second, Her heirs and successors according to law, in the office of Governor-General of the Commonwealth of Australia, and I will do right to all manner of people after the laws and usages of the Commonwealth of Australia, without fear or favour, affection or ill will. So help me God!

The oath or affirmation of office made by a prime minister, ministers and parliamentary secretaries when entering office is in wording that is not prescribed in the Constitution but determined by the prime minister of the day, and administered to them by the Governor-General. While there is no legal requirement for this, it has been the practice from the inauguration of the Commonwealth in 1901.[9]

1910 – State Debts – amended Section 105 to extend the power of the Commonwealth to take over pre-existing state debts to debts incurred by a state at any time.

1928 – State Debts – inserted Section 105A to ensure the constitutional validity of the Financial Agreement reached between the Commonwealth and State governments in 1927.

1946 – Social Services – inserted Section 51 (xxiiiA) to extend the power of the Commonwealth government over a range of social services.

1967 – Aborigines – amended Section 51 (xxvi) to extend the power of the Commonwealth government to legislate for people of any race to Aborigines; repealed Section 127 which stated that "In reckoning the numbers of the people of the Commonwealth, or of a State or other part of the Commonwealth, aboriginal natives shall not be counted."

Senate Casual Vacancies – part of the political fallout of the constitutional crisis of 1975; formalised the convention, broken in 1975, that when a casual vacancy arises in the Senate, the state parliament concerned, if it chooses to fill the vacancy, must choose the replacement from the same party as the departing Senator if that party still exists.

Referendums – amended Section 128 to allow residents of the Territories to vote in referendums, and be counted towards the national total.

Alongside the text of the Constitution, the Statute of Westminster and the Australia Acts, and letters patent issued by the Crown, conventions are an important aspect of the Constitution, which have evolved over the decades and define how various constitutional mechanisms operate in practice.

Conventions play a powerful role in the operation of the Australian constitution because of its set-up and operation as a Westminster system of responsible government. Some notable conventions include:

While the constitution does not formally create the office of Prime Minister of Australia, such an office developed a de facto existence as head of the cabinet. The Prime Minister is seen as the head of government.

While there are few constitutional restrictions on the power of the Governor-General, by convention the Governor-General acts on the advice of the Prime Minister.

However, because conventions are not textually based, their existence and practice are open to debate. Real or alleged violation of convention has often led to political controversy. The most extreme case was the Australian constitutional crisis of 1975, in which the operation of conventions was seriously tested. The ensuing constitutional crisis was resolved dramatically when the Governor-General Sir John Kerr dismissed the Labor Prime Minister Gough Whitlam, appointing Malcolm Fraser as caretaker Prime Minister pending the 1975 general election. A number of conventions were said to be broken during this episode. These include:

The convention that, when the Senator from a particular State vacates his or her position during the term of office, the State government concerned would nominate a replacement from the same political party as the departing Senator. This convention was allegedly broken by first the Lewis government of New South Wales and then by the Bjelke-Petersen government of Queensland who both filled Labor vacancies with an independent and a Labor member opposed to the Whitlam government respectively.[10]

Note: The convention was codified into the Constitution via the national referendum of 1977. The amendment requires the new Senator to be from the same party as the old one and would have prevented the appointment by Lewis, but not that by Bjelke-Petersen. However, the amendment states of the appointee that if "before taking his seat he ceases to be a member of that party...he shall be deemed not to have been so chosen or appointed". Bjelke-Petersen appointee Albert Patrick Field was expelled from the Labor Party before taking his seat and would therefore have been ineligible under the new constitutional amendment.[11]

The convention that, when the Senate is controlled by a party which does not simultaneously control the House of Representatives, the Senate would not vote against money supply to the government. This convention was allegedly broken by the Senate controlled by the Liberal-Country party coalition in 1975.[10]

The convention that a Prime Minister who cannot obtain supply must either request that the governor general call a general election, or resign. This convention was allegedly broken by Gough Whitlam in response to the Senate's unprecedented refusal.[12]

In line with the common law tradition in Australia, the law on the interpretation and application of the Constitution has developed largely through judgments by the High Court of Australia in various cases. In a number of seminal cases, the High Court has developed several doctrines which underlie the interpretation of the Australian Constitution. Some examples include:

Separation of powers – The three separate chapters dealing with the three branches of government implies a separation of powers, similar to that of the United States, but unusual for a government within the Westminster system.[13] Thus, for example, the legislature cannot purport to predetermine the legal outcome, or to change the direction or outcome, of a court case.

Division of powers – Powers of government are divided between the Commonwealth and the State governments, with certain powers being exclusive to the Commonwealth, others being concurrently exercised, and the remainder being held by the States.

Intergovernmental immunities – Although the Engineers' Case[14] held that there was no general immunity between State and Commonwealth governments from each other's laws, the Commonwealth cannot enact taxation laws that discriminated between the States or parts of the States (Section 51(ii)), nor enact laws that discriminated against the States, or such as to prevent a State from continuing to exist and function as a state (Melbourne Corporation v Commonwealth).[15]

The vast majority of constitutional cases before the High Court deal with characterisation: whether new laws fall within a permissible head of power granted to the Commonwealth government by the Constitution.[citation needed]

The Australian Constitution does not include a Bill of Rights. Some delegates to the 1898 Constitutional Convention favoured a section similar to the Bill of Rights of the United States Constitution, but the majority felt that the traditional rights and freedoms of British subjects were sufficiently guaranteed by the Parliamentary system and independent judiciary which the Constitution would create. As a result, the Australian Constitution has often been criticised for its scant protection of rights and freedoms.

Some express rights were, however, included:

Right to trial by jury – Section 80 creates a right to trial by jury for indictable offences against Commonwealth law. However, the Commonwealth is left free to make any offence, no matter how serious the punishment, triable otherwise than on indictment. As Justice Higgins said in R v Archdall (1928): "if there be an indictment, there must be a jury, but there is nothing to compel procedure by indictment".[16] In later cases, the High Court has split: some judges have attempted to find a right, on the basis that no constitutional provision may be understood in a way that renders it empty; others have thought that this would inject content, beyond the boundaries of judicial interpretation.[17] The Court has been flexible on the meaning of "jury": there will be a "jury", although not all members are male as would have been the Framers' understanding; but there will not a valid decision by a jury, if there is a majority verdict (even though that is permitted in some states). In practice, however, no major issue of abuse of this uncertainty has been raised.

Right to just compensation – Section 51(xxxi) creates a right to compensation "on just terms" for "acquisition of property" by the Commonwealth from any state or person.[18] The "acquisition of property", itself, is not restricted, but the High Court has understood the expression broadly so as to give a broad entitlement to compensation.

Right against discrimination on the basis of out-of-State residence – Section 117 prohibits disability or discrimination in one state against a resident of another state. This is interpreted widely: the restriction will be invalid if it treats an out-of-state resident more onerously than if they were resident within the state.[19] However, it does not prohibit states from imposing residential requirements where these are required by the State's autonomy and its responsibility to its people; a state may, for example, permit only residents to vote in state elections.

There are also some guaranteed freedoms, reasons why legislation that might otherwise be within power may nonetheless be invalid. These are not rights of individuals, but limitations upon legislative power. However, where legislation that would adversely affect an individual is found to be invalid for such a reason, the effect for the individual is similar to vindicating a right of that individual. There is one express "freedom".

Freedom of religion – Section 116 creates a freedom of religion, by prohibiting the Commonwealth (but not the states) from making "any law for establishing any religion, or for imposing any religious observance, or for prohibiting the free exercise of any religion". This section is based on the First Amendment to the US Constitution, but is weaker in operation. As the states retain all powers they had as colonies before federation, except for those explicitly given to the Commonwealth, this section does not affect the states' powers to legislate on religion. Section 116 has never been successfully invoked. A deterrent to invoking it is, as the High Court has found, the uncertain meaning of "religion".

There is also one implied right that is agreed upon by a majority judgment of the High Court. An implied right is one that is not written explicitly into the wording of the Constitution, but that the High Court has found to be implied by reading two or more sections together. The implied right of freedom of political communication is discussed below.

In addition to individual rights explicitly written into the Constitution and found to be implied by sections within it there is a final category of rights known as 'structural protections'. Rather than being individual rights, these are broad protections for the community as a whole, taken from the systems and principles created by and underpinning the text and structure of the Constitution as a whole. One of the more well-known of these protections is the community right to a democratically-elected parliament, commonly thought of as a limited "right" to vote, which is discussed below.

The following are implied rights or freedoms:

Implied freedom of political communication – In 1992 and 1994, the High Court found that the Constitution contained an "implied freedom of political communication", in a series of cases including Australian Capital Television[20] and Theophanous.[21] These were majority decisions, but the existence of the freedom was unanimously confirmed in Lange v ABC.[22] Rejecting wider suggestions in the earlier cases, Lange decided that the freedom can be found only in the "text and structure" of the Constitution and not by reference to any general legal or political principles, for example that of "democracy". In these terms, the freedom was found to be a necessary concomitant of the provision in Constitution sections 7 and 24 that the houses of the Commonwealth parliament shall be "chosen by the people"; the people must not be restricted from communicating with each other and with their representatives on all matters that may be relevant to that choice. The freedom was deemed to extend into the states and territories, on the basis that nationally there is a single sphere of political communication. The US First Amendment refers to "speech", which may be oral or written but is limited as to protection of non-verbal expression (such as burning a draft card). The High Court has avoided that limitation by preferring the broader term "communication".[23] Nonetheless, the freedom is not absolute: legislation that "burdens" the freedom of political communication will nevertheless be valid if it "proportionately" pursues some other legitimate purpose (such as public safety).

Implied right to vote – In 2007, in Roach v Electoral Commissioner,[24] the High Court held that Constitution ss7 and 24, by providing that members of the House of Representatives and the Senate be "directly chosen by the people", created a limited right to vote. This entailed the guarantee of a universal franchise in principle, and limited the Federal Parliament's legislative power to modify that universal franchise. In the case, a legislative amendment to disqualify from voting all prisoners (as opposed to only those serving sentences of three years or more, as it was before the amendment) was struck down as contravening that right. The structural protection of a democratically elected parliament prevents the Commonwealth from taking away the right to vote from sections of the community without a substantial and legitimate reason, but it does not grant each and every individual a "right" to vote in elections. The issue of implied right to vote came up again in Rowe v Electoral Commissioner.[25]

Attempts in High Court cases to find further implied rights or freedoms have not been successful. Implication of a freedom of association and a freedom of assembly, independently or linked to that of political communication, has received occasional judicial support but not from a majority in any case.

The term head of state does not appear in the Australian constitution. It is conventionally acknowledged to be the Queen, since the governor-general and the state governors are defined as her "representatives".[26][27] However, since the governor-general is given important constitutional powers, the governor-general is often referred to as head of state in political and media discussion, such as by Malcolm Turnbull and Kevin Rudd.

Amongst the amendments proposed to the Constitution over the years, two proposals for major change have been prominent in recent decades, and both were considered, and defeated, in the 1999 referendum.

While a pro forma preamble prefaces the Imperial Commonwealth of Australia Constitution Act 1900, the Australian Constitution itself does not contain a preamble. There have been some calls for the insertion of such a section to express the spirit and aspirations embodied in the constitution. However, there has been fierce opposition, usually on the basis of the content of the preamble, as well as possible legal ramifications of this text. In 1999, a proposed preamble, principally authored by John Howard, the then Prime Minister, was defeated in a referendum held concurrently with the Republic referendum. The "Yes" vote (in favour of the insertion of the preamble) did not achieve a majority in any of the six states.

At various times since Federation, debates have occurred over whether Australia should become a republic. On 6 November 1999, Australians rejected a proposal to remove the Queen and replace the Governor-General with a President appointed by a two-thirds majority of the members of the Commonwealth Parliament.

Constitution Day is celebrated on 9 July,[28] the date the Constitution became law in 1900. The date is not a public holiday. Constitution Day was first held on 9 July 2000 to mark the centenary of the Constitution in the lead up to the Centenary of Federation, although commemorations were low key and were not widely held after 2001. Constitution Day was revived in 2007 and is jointly organised by the National Archives of Australia, which holds the original Constitution documents, and the Department of Immigration and Citizenship.[29]

^In Australian law, legislation which was enacted by the British parliament and which has or had effect in Australia by paramount force (or was subsequently received into Australian law) is referred to as "imperial" law, denoted with the "(Imp)" abbreviation when citing legislation by its short title.

"Full text download".(525 KB) from ComLaw – The Constitution as in force on 1 June 2003 together with proclamation declaring the establishment of the Commonwealth, letters patent relating to the Office of Governor-General, Statute of Westminster Adoption Act 1942, Australia Act 1986.ISBN 0-642-78285-7.

Commonwealth of Australia Constitution Act (The Constitution), as amended and annotated, Prepared by the Office of Legislative Drafting, Attorney-General's Department, Canberra, as at September 2013 [2]